四川盆地中部下二叠统茅口组岩溶储集层地震预测

Karst reservoirs seismic prediction of Lower Permian Maokou Formation in central Sichuan Basin,SW China

基于近年来新的测井和地震资料,综合利用地球物理技术对四川盆地中部(川中地区)下二叠统茅口组岩溶储集层开展研究。定量岩石物理建模和分析表明,随着孔隙度、泥质含量以及含气饱和度的增加,岩溶储集层的纵、横波速度和密度均呈减小的趋势。基于岩石物理模型的地震正演分析结果证实,川中地区岩溶储集层在茅口组顶面具有弱振幅、低频率的"暗点"地震反射特征。通过地震属性和波阻抗反演预测了4个规模有利岩溶储集层发育带。综合评价认为川中地区茅口组岩溶储集层具备形成上倾岩性尖灭型岩性气藏的成藏条件,预测射洪西部和盐亭地区为川中地区最为有利的勘探区带。

Based on the new well logging and seismic data of recent years in central Siehuan Basin, the comprehensive study of the karst reservoirs in the Lower Permian Maokou Formation was carried out using new geophysical technology. The quantitative rock physical modeling and analysis demonstrated that the velocity and density of the reservoir decrease with the increase of porosity, shale volume and gas saturation. Seismic forward modeling analysis based on rock physical modeling confirmed that the reflection characteristics of the karst reservoirs show ＇dim point＇ at top of the Maokou Formation, which is weak amplitude and low frequency. Through seismic attributes and wave impedance inversion, four large areas of favorable karst reservoirs are predicted. Based on the comprehensive evaluation, it is thought that karst lithologic reservoirs in up-dip direction can be formed, and the west to Shehong and Yanting are the most favorable exploration areas in the central Sichuan Basin.